Design and preparation of polytetrafluoroethylene/carbon (PTFE/C) composite membrane‐equivalent foam for gravity‐driven emulsion separation

Abstract

Herein, a concept of the membrane‐equivalent‐foam (MEF) with equivalent characteristics of a separated‐multi‐layer membrane was proposed and elaborated to mitigate the conflict between efficiency and selectivity in emulsion separation. Porous PTFE/C composite MEF with a two‐level microporous structure (bubble pores and ice‐templated pores) was prepared successfully, which was derived from a PTFE/glutaraldehyde‐crosslinked‐polyvinyl alcohol (PVAG) composite foam green body. PVAG based in‐situ carbon was analyzed as composed mainly of amorphous carbon. The bubble pores were observed to be interconnected by ice‐templated pores. The porosity of the porous PTFE/C composite MEF reached a remarkable value of 73.35%. Corresponding to m(PTFE)/m(PVA) value of 14/1, 12/1, 10/1 and 8/1, the average pore sizes of the bubble pores were 32.99 μm, 44.31 μm, 47.33 μm, 48.01 μm, and the average sizes of ice‐templated pores were about 2.24 μm, 2.77 μm, 3.02 μm and 3.47 μm, respectively. Meanwhile, the porous PTFE/C composite MEF exhibited near superhydrophobicity in air and the superhydrophobicity under oil. In gravity‐driven W/O emulsion separation tests, the oil flux was up to 3541 L/(h∙m2), and the separation efficiency reached more than 99.52%. After 20 cycles of testing, the oil flux and separation efficiency remained stable. The membrane‐equivalent thickness of the samples from PTFE/C‐m1 to PTFE/C‐m4 were below 3.47 nm, 4.26 nm, 0.58 nm and 0.30 nm, respectively, which was about 10‐7~10‐6 times lower than the height of porous PTFE/C composite MEF. It is reasonable to believe that porous PTFE/C composite MEF could effectively mitigation of the “trade‐off” effect.This article is protected by copyright. All rights reserved.